Abstract

R-matrix
calculations on electron collisions with CO are reported whose aim is to identify any
higher-lying resonances above the well-reported and lowest 2Π resonance at
about 1.6 eV. Extensive tests with respect to basis sets, target models and scattering
models are performed. The final results are reported for the larger cc-pVTZ basis set
using a 50 state close-coupling (CC) calculation. The Breit-Wigner eigenphase sum and the
time-delay methods are used to detect and fit any resonances. Both these methods find a
very narrow 2Σ+ symmetry Feshbach-type resonance very close to the
target excitation threshold of the b 3Σ+ state which lies at 12.9 eV in the calculations. This
resonance is seen in the CC calculation using cc-pVTZ basis set while a CC calculation
using the cc-pVDZ basis set does not produce this feature. The electronic structure of
CO− is analysed
in the asymptotic region; 45 molecular states are found to correlate with states
dissociating to an anion and an atom. Electronic structure calculations are used to study
the behaviour of these states at large internuclear separation. Quantitative results for
the total, elastic and electronic excitation cross sections are also presented. The
significance of these results for models of the observed dissociative electron attachment
of CO in the 10 eV region is discussed.

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